1. Field of the Invention
One or more aspects of the invention generally relate to texture mapping, and more particularly to processing of texture data stored as a chart.
2. Description of the Related Art
Conventional graphics processing applies texture maps including normal vectors and color data to lower resolution three-dimensional (3D) models, i.e., 3D models with fewer graphics primitives, to produce images that appear similar to images produced using high resolution models. FIG. 1A illustrates prior art 3D models, a high resolution 3D model 101 and a lower resolution 3D model 102. When a normal vector texture is applied to model 102 during shading, model 102 may appear similar to model 101. Because model 102 includes fewer faces (graphics primitives) rendering performance is improved although the image quality may decrease.
Graphics artists are able to create 3D models and paint a texture, including color data, onto the model using a 3D paint system. The graphics artists may also partition the 3D model into specific portions, such as biological features of characters, e.g., ear, leg, tail, or the like. In addition to a texture map including color data a normal vector texture map may be generated for model 102. The texture maps applied to faces of the 3D model are each stored as an atlas including one or more charts, where each chart corresponds to a specific portion of model 102 and is homeomorphic to a disc. The charts are parameterized and packed into texture space to produce the atlas.
FIG. 1B illustrates a prior art texture map atlas 105 including several charts that represent normal vector data for model 102. When a texture map is applied to a model, such as model 102 discontinuities may appear at seams between faces within the model. In particular, discontinuities may appear when texture data is applied from different charts on either side of a seam when the faces forming the seam are not adjacent in texture space. In particular, when a texel sampling position, such as a texel center, on a chart perimeter is not within a chart boundary, a sample corresponding to the texel may not be accurate, resulting in a discontinuity along a seam.
In some conventional systems texture data is copied from adjacent texels that are within the chart boundary to provide texture data for a texel whose center is not within the chart boundary. Although, copying the texture data may improve the appearance of a seam, discontinuities may still be visible, particularly when the texture data is normal vector data.
Accordingly, there is a need to reduce the discontinuities that may appear when any type of texture data from non-adjacent charts is applied to a model.